Polyphenylene ether resins (hereinafter referred to as PPE) are useful as molding resins because of their excellent thermal, mechanical and electrical properties, but the range of their utility is limited due to insufficiency in moldability, organic solvent resistance, and impact resistance. Incorporation of other resins with PPE has been proposed to overcome these disadvantages. For example, U.S. Pat. No. 3,383,435 suggests improving moldability of PPE by incorporation of a styrene polymer, but improvement in organic solvent resistance is not achieved.
Studies have also been made on various blends of PPE and olefin resins having excellent organic solvent resistance. For example, JP-B-42-7069 (the term "JP-B" as used herein means an "examined published Japanese patent application") proposes a blend of an olefin resin and PPE, but the blend does not always reach high standards of organic solvent resistance and mechanical strength as demanded in industry.
Compounding, for example, a styrene-butadiene block copolymer or a hydrogenation product thereof with a blend of PPE and an olefin resin for the purpose of improving compatibility between these two resin components has been proposed as disclosed in JP-A-53-71158 (U.S. Pat. No. 4,145,377), JP-A-54-88960, U.S. Pat. No. 4,166,055, U.S. Pat. No. 4,239,673, JP-A-59-100159, and EP-A-115712 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). In the compositions proposed, however, since the proportion of the olefin resin is small and PPE substantially forms a continuous phase, organic solvent resistance possessed by olefin resins is not sufficiently manifested.
JP-A-58-103557 (U.S. Pat. No. 4,383,082) and JP-A-60-76547 (EP-A-133487) disclose PPE resin compositions containing at least 20% by weight of an olefin resin and a compatibilizer, for example, a di-block copolymer of an alkenyl aromatic compound and a conjugated diene or a hydrogenation product thereof. Although these compositions exhibit improved tensile characteristics and non-brittleness, they do not sufficiently achieve required levels of rigidity and heat resistance.
JP-A-63-128021 discloses a PPE resin composition comprising (a) an alcoholic hydroxyl-modified PPE obtained by addition of ethylene oxide to PPE, (b) a maleic anhydride-modified styrene-grafted polyolefin, (c) unmodified PPE, and (d) polypropylene. However, it is difficult to prepare OH-modified PPE copolymer (a) with constant properties by addition of ethylene oxide, and molded articles obtained from the resulting resin composition have reduced strength.
Further, incorporation of a polyamide resin with PPE has been proposed to provide various compositions in which the disadvantages of the two resins are compensated for by each other while retaining their own advantages. For example, compositions prepared by merely mixing these two resin components in a molten state are disclosed in U.S. Pat. No. 3,379,792, JP-B-45-997, U.S. Pat. No. 4,338,421, and JP-B-59-41663. However, since PPE is essentially incompatible with polyamides, such a mere polymer blend undergoes phase separation on molding due to poor interfacial affinity, failing to have excellent mechanical strength.
Methods proposed to date for improving compatibility between polyamide resins and PPE include compounding a compound having a carbon-carbon double bond and any of a carboxyl group, an acid anhydride group, an acid amide group, an imido group, a carboxylic ester group, an epoxy group, an amino group, and a hydroxyl group in the. molecule thereof as disclosed, e.g., in JP-A-56-26913; compounding a liquid diene polymer as disclosed, e.g., in JP-A-57-10642; compounding a compound having an oxirane ring in the molecule thereof and/or a condensed high polymer obtained from a dihydric phenol and epichlorohydrin as disclosed, e.g., in JP-A-56-47432 (above fore JP-A No. incorporated in U.S. Pat. No. 4,315,066); compounding an organic phosphoric ester as disclosed, e.g., in JP-A-60-58463 (EP-A-129825); and compounding a compound having a carbon-silicon bond, either one of a halogen atom and an alkoxy group, and any one of an alkyl group, a vinyl group, an acrylic group, a methacrylic group, an amino group, an epoxy group, and a mercapto group in the molecule thereof as disclosed in JP-A-62-232455 and JP-B-59-33614 (U.S. Pat. No. 4,339,376).
These methods aim toward the improvement in compatibility through activation of the terminal phenolic hydroxyl group or the methyl group in the side chain of PPE by melt-kneading in the presence of a third component. However, because the terminal phenolic hydroxyl group or the methyl group in the side chain of PPE essentially has limited reactivity, these methods often fail to sufficiently improve compatibility of PPE with polyamide resins. Besides, the third component added remains unreacted in the resulting modified PPE, which causes unfavorable problems such as poor appearance of molded articles due to volatilization of such an unreacted substance during molding and color instability due to deteriorated hue of the molded articles. In addition, the resulting resin compositions are still insufficient in mechanical strength.
Furthermore, it is known to incorporate saturated polyester resins into PPE as disclosed, e.g., in JP-B-51-21664, JP-A-49-50050, JP-A-49-75662, and JP-A-59-159847. However, in such mere blends having a two-phase structure, the affinity in the interface between the two phases of PPE and a saturated polyester resin is insufficient due to poor compatibility so that the two phases hardly form a uniform and fine dispersion. Such a polymer blend is apt to undergo delamination under a shearing stress on molding, such as injection molding, and the resulting molded articles have a deteriorated appearance or suffer from defects in the interface of two phases. Therefore, a composition excellent in mechanical characteristics, e.g., dimensional precision, heat resistance and rigidity, and physical characteristics, e.g., solvent resistance, cannot be obtained.
Approaches proposed to date for improving compatibility between PPE and saturated polyester resins include a method of using a modified PPE obtained by reacting PPE with a compound containing a carbon-carbon double bond or a carbon-carbon triple bond and at least one of a carboxyl group, an acid anhydride group, an acid amide group, an epoxy group, a hydroxyl group, etc. as disclosed in JP-A-62-257958, JP-A-63-54427 (U.S. Pat. Nos. 4,755,566 and 4,889,889), and JP-W-63-500803 (WO-A-8700540) (the term "JP-W" as used herein means an "unexamined published international patent application"); a method of using an alkoxysilyl-modified PPE as disclosed in JP-W-63-503392 (WO-A-8707279); a method of using an oxazoline-modified PPE as disclosed in JP-A-2-187453; a method of using a polyester modified with hydroxyl- or carboxyl-terminated polystyrene as disclosed in JP-A-2-170852 (EP-A-365841); a method of compounding a hydroxycarboxylic acid as disclosed in JP-A-2-129259 (EP-A-368283); a method of using a hydroxyalkylated PPE obtained by reacting PPE with a bis(hydroxyalkyl) maleate, which is melt-kneaded with polybutylene terephthalate as disclosed in U.S. Pat. No. 4,746,708 and WO 87/07279; and a method of using a hydroxyalkylated PPE obtained by reacting PPE with terephthaloyl chloride and then reacting the product with a diol, which is melt-kneaded with polybutylene terephthalate as disclosed in U.S. Pat. No. 4,746,708 and WO 87/07279. In many cases, however, these techniques are still unsatisfactory for improving compatibility between PPE and saturated polyester resins, and the resulting resin compositions do not have sufficient mechanical characteristics and still need further improvements.